Observability of paramagnetic NMR signals at over 10 000 ppm chemical shifts

Jonas C. Ott; Elizaveta A. Suturina; Ilya Kuprov; Joscha Nehrkorn; Alexander Schnegg; Markus Enders; Lutz Gade

doi:10.1002/ange.202107944

Observability of paramagnetic NMR signals at over 10 000 ppm chemical shifts

Jonas C. Ott, Elizaveta A. Suturina, Ilya Kuprov, Joscha Nehrkorn, Alexander Schnegg, Markus Enders, Lutz Gade

Department of Chemistry

Research output: Contribution to journal › Article › peer-review

Abstract

We report an experimental observation of 31 P NMR resonances shifted by over 10 000 ppm (meaning percent range, and a new record for solutions), and similar 1 H chemical shifts, in an intermediate-spin square planar ferrous complex [ t Bu (PNP)Fe–H], where PNP is a carbazole based pincer ligand. Using a combination of electronic structure theory, nuclear magnetic resonance, magnetometry, and terahertz electron paramagnetic resonance, the influence of magnetic anisotropy and zero-field splitting on the paramagnetic shift and relaxation enhancement is investigated. Detailed spin dynamics simulations indicate that, even with relatively slow electron spin relaxation ( T 1 ~ 10 -11 s), it remains possible to observe NMR signals of directly metal-bonded atoms because pronounced rhombicity in the electron zero-field splitting reduces nuclear paramagnetic relaxation enhancement.

Original language	English
Pages (from-to)	23038-23046
Journal	Angewandte Chemie
Volume	133
Issue number	42
Early online date	5 Aug 2021
DOIs	https://doi.org/10.1002/ange.202107944
Publication status	Published - 11 Oct 2021

Bibliographical note

Funding Information
The authors thank Heidelberg University for funding this work and acknowledge support by the state of Baden-Württemberg through bwHPC and the German Research Foundation through Grant INST 40/575-1 FUGG (JUSTUS 2 cluster). We thank Dr. Bernd Simon (European Molecular Biology Laboratory, Heidelberg) for the provision of measuring time at the 800 MHz NMR spectrometer. We thank Dr. Thomas Lohmiller, Dr. Karsten Holldack and Dirk Ponnwitz (HZB) for help with the FD-FT THz-EPR measurements at BESSY II, Andreas Göbels (MPI CEC) for conducting the SQUID magnetometry measurements and Dr. Eckhard Bill (MPI CEC) for making available a program for the simulation of SQUID magnetometry data and help with the data interpretation. Allocation of FD-FT THz-EPR beam time by Helmholtz Zentrum Berlin für Materialien und Energie (HZB) is gratefully acknowledged. EAS thanks the University of Bath HPC facility for the computational resources. Open access funding enabled and organized by Projekt DEAL.

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title = "Observability of paramagnetic NMR signals at over 10 000 ppm chemical shifts",

abstract = "We report an experimental observation of 31 P NMR resonances shifted by over 10 000 ppm (meaning percent range, and a new record for solutions), and similar 1 H chemical shifts, in an intermediate-spin square planar ferrous complex [ t Bu (PNP)Fe–H], where PNP is a carbazole based pincer ligand. Using a combination of electronic structure theory, nuclear magnetic resonance, magnetometry, and terahertz electron paramagnetic resonance, the influence of magnetic anisotropy and zero-field splitting on the paramagnetic shift and relaxation enhancement is investigated. Detailed spin dynamics simulations indicate that, even with relatively slow electron spin relaxation ( T 1 ~ 10 -11 s), it remains possible to observe NMR signals of directly metal-bonded atoms because pronounced rhombicity in the electron zero-field splitting reduces nuclear paramagnetic relaxation enhancement.",

author = "Ott, {Jonas C.} and Suturina, {Elizaveta A.} and Ilya Kuprov and Joscha Nehrkorn and Alexander Schnegg and Markus Enders and Lutz Gade",

note = "Funding Information The authors thank Heidelberg University for funding this work and acknowledge support by the state of Baden-W{\"u}rttemberg through bwHPC and the German Research Foundation through Grant INST 40/575-1 FUGG (JUSTUS 2 cluster). We thank Dr. Bernd Simon (European Molecular Biology Laboratory, Heidelberg) for the provision of measuring time at the 800 MHz NMR spectrometer. We thank Dr. Thomas Lohmiller, Dr. Karsten Holldack and Dirk Ponnwitz (HZB) for help with the FD-FT THz-EPR measurements at BESSY II, Andreas G{\"o}bels (MPI CEC) for conducting the SQUID magnetometry measurements and Dr. Eckhard Bill (MPI CEC) for making available a program for the simulation of SQUID magnetometry data and help with the data interpretation. Allocation of FD-FT THz-EPR beam time by Helmholtz Zentrum Berlin f{\"u}r Materialien und Energie (HZB) is gratefully acknowledged. EAS thanks the University of Bath HPC facility for the computational resources. Open access funding enabled and organized by Projekt DEAL. ",

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AU - Ott, Jonas C.

AU - Suturina, Elizaveta A.

AU - Kuprov, Ilya

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AU - Schnegg, Alexander

AU - Enders, Markus

AU - Gade, Lutz

N1 - Funding Information The authors thank Heidelberg University for funding this work and acknowledge support by the state of Baden-Württemberg through bwHPC and the German Research Foundation through Grant INST 40/575-1 FUGG (JUSTUS 2 cluster). We thank Dr. Bernd Simon (European Molecular Biology Laboratory, Heidelberg) for the provision of measuring time at the 800 MHz NMR spectrometer. We thank Dr. Thomas Lohmiller, Dr. Karsten Holldack and Dirk Ponnwitz (HZB) for help with the FD-FT THz-EPR measurements at BESSY II, Andreas Göbels (MPI CEC) for conducting the SQUID magnetometry measurements and Dr. Eckhard Bill (MPI CEC) for making available a program for the simulation of SQUID magnetometry data and help with the data interpretation. Allocation of FD-FT THz-EPR beam time by Helmholtz Zentrum Berlin für Materialien und Energie (HZB) is gratefully acknowledged. EAS thanks the University of Bath HPC facility for the computational resources. Open access funding enabled and organized by Projekt DEAL.

PY - 2021/10/11

Y1 - 2021/10/11

N2 - We report an experimental observation of 31 P NMR resonances shifted by over 10 000 ppm (meaning percent range, and a new record for solutions), and similar 1 H chemical shifts, in an intermediate-spin square planar ferrous complex [ t Bu (PNP)Fe–H], where PNP is a carbazole based pincer ligand. Using a combination of electronic structure theory, nuclear magnetic resonance, magnetometry, and terahertz electron paramagnetic resonance, the influence of magnetic anisotropy and zero-field splitting on the paramagnetic shift and relaxation enhancement is investigated. Detailed spin dynamics simulations indicate that, even with relatively slow electron spin relaxation ( T 1 ~ 10 -11 s), it remains possible to observe NMR signals of directly metal-bonded atoms because pronounced rhombicity in the electron zero-field splitting reduces nuclear paramagnetic relaxation enhancement.

AB - We report an experimental observation of 31 P NMR resonances shifted by over 10 000 ppm (meaning percent range, and a new record for solutions), and similar 1 H chemical shifts, in an intermediate-spin square planar ferrous complex [ t Bu (PNP)Fe–H], where PNP is a carbazole based pincer ligand. Using a combination of electronic structure theory, nuclear magnetic resonance, magnetometry, and terahertz electron paramagnetic resonance, the influence of magnetic anisotropy and zero-field splitting on the paramagnetic shift and relaxation enhancement is investigated. Detailed spin dynamics simulations indicate that, even with relatively slow electron spin relaxation ( T 1 ~ 10 -11 s), it remains possible to observe NMR signals of directly metal-bonded atoms because pronounced rhombicity in the electron zero-field splitting reduces nuclear paramagnetic relaxation enhancement.

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DO - 10.1002/ange.202107944

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JF - Angewandte Chemie

IS - 42

ER -

Observability of paramagnetic NMR signals at over 10 000 ppm chemical shifts

Abstract

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